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Results for “Absorbable Implants”

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PubMed2001

Causes of the clinical tissue response to polyglycolide and polylactide implants with an emphasis on the knee.

The causes of a clinical tissue response to self-reinforced polyglycolide (SR-PGA) and self-reinforced polylactide (SR-PLLA) implants were studied in the first 2500 polymeric fixations. The incidence was 8.0% in fixations with implants made of SR-PGA (n = 1879) and 0% in SR-PLLA fixations (n = 621). A small number of fixations per site seemed to increase the incidence of a tissue response. In diagnoses involving over 50 fixations, except for ankle fractures, the incidence was 4.2%. The site of fixation influenced the incidence; the lowest incidence was seen for radial head fracture fixation (1.1%). The aromatic dye which has not been used since 1988 in the SR-PGA implant increased the response. A large total implant volume and a large number of implants increased the incidence of a tissue response. In the knee (n = 131), the incidence of a clinical tissue response was 4.3%, with four fluid accumulations and one synovitis of the knee after fixation with SR-PGA implants.

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PubMed2000

In vitro reconstructed dermis implanted in human wounds: degradation studies of the HA-based supporting scaffold.

The objective of the present study was to demonstrate the safety and efficacy of a dermal replacement for cutaneous wounds of diverse origin. Autologous fibroblasts were cultured in fleece scaffolds made from benzyl esters of hyaluronic acid and applied onto cutaneous lesions. The cases presented are (1) skin removal for multiple epithelioma and (2) chronic deep decubitus ulcer. Dermal-like tissue applied by the surgeon elicited no adverse reactions, and was fully integrated and well-vascularized by 1-3 weeks. In Case 1, the material was fully integrated after 1 week, and after 3 weeks an epidermal autograft was overlaid which showed good take with excellent integration observed after 4 weeks. At 12 months, skin demonstrated visual normo-elastic properties and no signs of excessive scarring. In Case 2, 2-3 weeks after the dermal implant was applied, the wound was invaded with granulation tissue and healing occurred by secondary intention. The ulcer was healed by 8 weeks, with the biomaterial completely resorbed and a complete re-epithelialization over the dermal-like tissue. These results suggest that autologous fibroblast culture in hyaluronan-derived scaffolds may be successfully grafted in diverse cutaneous pathologies and constitute a suitable bed for further epidermal implantation.

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PubMed1998

Fixation of zygomatic fractures with a new biodegradable copolymer osteosynthesis system. Preliminary results.

In a prospective study, a new biodegradable osteosynthesis material for the facial skeleton has been used in 27 patients with zygomatic fractures. In the six-month follow-up period, the first ten patients showed clinically and radiologically uneventful healing of bone. There were no implant-related complications. The main advantages of the new material are its malleability when heated, enabling fast adaptation to the bone surface, and the avoidance of a second operation for implant removal.

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PubMedDate not supplied

Cranio-caudal differences in granulation tissue formation: an experimental study in the rat.

This study examined potential regional differences in the deposition of granulation tissue in cellulose sponges placed in the dorsum of rats. Four cellulose sponge implants, 10 x 10 x 5 mm in size, two in cranial and two in caudal positions, were used to induce granulation tissue formation in the back of the rat. A cranio-caudal difference in connective tissue formation was assessed from 1 to 24 weeks after implantation. Granulation tissue ingrowth, measured histomorphometrically, was enhanced at 2 weeks and the surrounding capsule was thinner from 1 to 3 weeks in implants located in the cranial part of the back. In the cranial position, the number of fibroblasts, assessed semiquantitatively, was higher and the ratio of inflammatory cells to fibroblasts lower at 2-3 weeks. Also, the ratio of hydroxyproline content to total nitrogen content was higher after the first week in cranial specimens. Thus, a distinct cranio-caudal difference in the proliferative phase was observed. These results show the obvious practical considerations underlying the need for randomization or comparison between implants from exactly corresponding cranio-caudal locations.

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PubMed2006

Collagen-GAG scaffolds grafted onto myocardial infarcts in a rat model: a delivery vehicle for mesenchymal stem cells.

Various cell delivery methods have been investigated for cell transplantation treatment of cardiac infarcts. In this study, we investigated a type I collagen-glycosaminoglycan (GAG) scaffold for the implantation of adult bone marrow-derived mesenchymal stem cells (MSCs) into the infarcted region in the rat heart. The objective was to evaluate the tissue response to collagen-GAG scaffolds prepared using 2 cross-linking methods. The left coronary artery of female Wistar rats was occluded for 60 min, followed by reperfusion. One week later, the infarcted region was implanted with (1) collagen-GAG scaffolds cross-linked by dehydrothermal treatment alone (DHT; n = 10); (2) collagen-GAG scaffolds cross-linked by DHT followed by carbodiimide treatment (EDAC; n = 8); or (3) DHT cross-linked collagen-GAG scaffolds seeded with bromodeoxyuridine (BrdU)-labeled allogeneic MSCs (cell-scaffold; n = 9). Shamoperated rats served as controls (n = 4). Specimens were harvested 3 weeks after the implantation surgery. The tissue response was evaluated histomorphometrically and by immunohistochemistry to track the BrdU-labeled MSCs. Most of the DHT cross-linked collagen-GAG scaffolds degraded, whereas the scaffolds in the EDAC group appeared to be largely intact. There were no signs of acute inflammation in any of the groups. A substantial amount of neovascularization was seen in the infarcted region in the implant groups and in the scaffolds themselves. BrdU-positive cells appeared both in the degraded scaffold and the infarct region. DHT cross-linked collagen-GAG scaffolds warrant continued investigation as delivery vehicles for implantation of cells into infarcted cardiac tissue.

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PubMed2003

Antibacterial poly(D,L-lactic acid) coating of medical implants using a biodegradable drug delivery technology.

OBJECTIVES: Biomaterial-associated bacterial infections present common and challenging complications with medical implants. The purpose of this study was to determine the antibacterial properties of a low molecular weight biodegradable poly(D,L-lactic acid) coating with integrated antibiotics gentamicin and teicoplanin. METHODS: Coating of Kirschner-wires was carried out by a solvent casting technique under aseptic conditions with and without incorporated antibiotics. Release kinetics of gentamicin and teicoplanin were studied in phosphate-buffered saline. Initial bacterial adhesion of Staphylococcus epidermidis on coated and bare implants was determined by radiolabelling and counts of detached viable organisms. RESULTS: The incorporated antibiotics showed a continuous release over a period of at least 96 h with an initial peak of release in the first 6 h. Attachment of non-viable microorganisms, detected by radiolabelled bacteria, was increased significantly by the polymer coatings (P < 0.05). In contrast, the number of viable bacteria was reduced by the pure polymer (P < 0.01) and further by the polymer-antibiotic combinations (P < 0.05). CONCLUSIONS: Poly(D,L-lactic acid) coating of implants could offer new perspectives in preventing biomaterial-associated infections. Combinations with other drugs to formulate custom-tailored implant surfaces are feasible.

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PubMed2006

Cell-based tissue engineering for lung regeneration.

Emphysema is a chronic lung disease characterized by alveolar enlargement and tissue loss. Tissue engineering represents an attractive potential for regeneration of several organ systems. The complex three-dimensional architectural structure of lung parenchyma requiring connections of alveolar units to airways and the pulmonary circulation makes this strategy less optimistic. In the present study, we used Gelfoam sponge as a scaffold material, supplemented with fetal rat lung cells as progenitors, to explore the potential application of cell-based tissue engineering for lung regeneration in adult rats. After injection into lung parenchyma, the sponge showed porous structures similar to alveolar units. It did not induce severe local inflammatory response. Fetal lung cells in the sponge were able to survive in the adult lung for at least 35 days, determined by CMTMR [5-(and-6)-{[(4-chloromethyl)benzoyl]amino}tetramethylrhodamine] labeling. Proliferation of cells within the sponge was demonstrated in vivo by bromodeoxyuridine (BrdU) labeling. Cells formed "alveolar-like structures" at the border between the sponge and the surrounding lung tissue with positive immunohistochemical staining for epithelial and endothelial cells. Neovascularization of the sponge was demonstrated with India ink perfusion. The sponge degraded after several months. This study suggests that cell-based tissue engineering possesses the potential to regenerate alveolar-like structures, an important step towards our ultimate goal of lung regeneration.

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PubMedDate not supplied

A histomorphometric evaluation of factors influencing the healing of bony defects surrounding implants.

PURPOSE: The authors' aim was to perform a histomorphometric study of the healing of bone defects created adjacent to titanium and hydroxyapatite (HA) -coated implants and covered with either a resorbable or a nonresorbable membrane in combination with different filler materials and to evaluate to what degree coating, membrane, and/or filler influenced the healing of the defects. MATERIALS AND METHODS: Posterior teeth were extracted from the mandibles of 10 baboons, and 12 implants were placed in each animal in the edentulous areas. The implants were either titanium or HA-coated, the membranes were either Vicryl, Gore-Tex, or Resolut, and the filler was either demineralized freeze-dried bone (DFDB), autogenous bone, or Biocoral. The implants were observed for either 3, 6, 9, 12, or 18 months. The volume of newly generated tissue and the relative contribution of bone, marrow, and filler were evaluated, as was relative extension of resorption, formation, and quiescent surface. RESULTS: The results indicated that autogenous bone is still the gold standard, but both the DFDB and Biocoral compared favorably to it. Both filler materials were being gradually replaced by bone; this process was not yet finished at 18 months postsurgery. DISCUSSION: Since even the sterilization of DFDB cannot exclude the possibility of a disease transmission, it is important to find an appropriate substitute. Both filler and membranes contributed to the re-establishment of the original volume; better results were achieved with the Vicryl and Gore-Tex membranes than with the Resolut. Biocoral can be considered an effective material. CONCLUSION: A bony defect is not necessarily a contraindication for the placement of an implant. (More than 50 references.)

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PubMed2005

Transforming growth factor-beta 1 (TGF-beta1) prevents the age-dependent decrease in bone formation in human osteoblast/implant cultures.

Titanium implants have been extensively used in orthopedic surgery and dentistry. Most of the patients who receive such implants are elderly with a compromised ability to heal and form new bone. By using an in vitro osteoblast/implant culture system, the potency of TGF-beta1 in enhancing mineralization of human osteoblast cultures from elderly subjects was investigated in this study. Primary human osteoblast (HOB) cells obtained from different age group human subjects [Young (Y), Middle (M), and Old (O)] were cultured on Ti alloy (Ti-6Al-4V) disks with or without continuous administration of 0.2 ng/mL TGF-beta1 in the medium for 2 or 4 weeks. TGF-beta1 significantly (p < 0.05) increased calcium content and the size of calcified nodules on implant disks in the O group, but had no effect on the Y or M groups. The number of calcified nodules was not different with or without TGF-beta1 in all age groups. As measured by Northern blot analysis and RT-PCR, TGF-beta1 significantly increased the expression of bone-specific extracellular matrix proteins, including alkaline phosphatase, Type I collagen, bone sialoprotein and osteocalcin, after both 2 and 4 weeks in the O group but not in the Y group. In conclusion, TGF-beta1 enhances mineralization on implant materials of osteoblast cultures from elderly human subjects.

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PubMed2006

Closing capacity of cranial bone defects using porous calcium phosphate cement implants in a rabbit animal model.

Calcium phosphate (Ca-P) cement is a well established material for bone repair. The bone biological properties of Ca-P cement can even be further improved by creating porosity in the material. The current study aimed on the evaluation of the osteoconductive behavior of porous Ca-P cement. Therefore, circular defects (6, 9, and 15 mm in diameter) were created in the cranium of 3 months old rabbits and filled with porous Ca-P cement implants. The total porosity of implants was calculated to be 71, 74 and 74% respectively and the average pore diameter was 150 microm. In addition, empty control defects were prepared. After 12 weeks implantation time the animals were sacrificed and radiographic, histological, and histomorphometrical evaluation was performed. The Critical Size Defect (CSD) of this species at this location for an implantation time of 12 weeks was confirmed to be 15 mm. Bone was observed to be present over and through almost all porous Ca-P cement implants. Only, in one out of eight animals with a 15 mm implant complete bone bridging of the defect did not occur. The size of the defect was found not to affect the total percentage of bone formation in the cement; (17 +/- 7)%, (18 +/- 6)% and (17 +/- 3)% for respectively 6, 9, and 15 mm diameter implants. We concluded that porous Ca-P cement is an excellent osteoconductive material in non weight bearing situations and complete bridging of a critical sized skull defect occurs in this rabbit model after 12 weeks of implantation.

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PubMed2005

Bone compaction enhances fixation of hydroxyapatite-coated implants in a canine gap model.

Primary cementless joint replacement depends partly on the ability of bone to heal into those areas of an inserted implant where a gap to surrounding bone initially exists. A new bone preparation technique, compaction, has enhanced gap-healing around grit-blasted implants without osteo-conductive properties. However, hydroxyapatite (HA) porous-coated implants with osteo-conductive properties are often inserted clinically to enhance gap healing and implant fixation. It is unknown whether the osteo-conductive properties of HA porous-coated implants might overwhelm the beneficial effects of compaction on gap healing. Therefore, we compared the compaction technique with the conventional bone-removing technique, drilling, using HA porous-coated implants in a canine gap model. HA porous-coated titanium implants were bilaterally inserted into oversized cavities of the proximal humeri of seven dogs. Each dog served as its own control. Thus, one humerus had the implant cavity prepared with compaction, the other with drilling. Two weeks after surgery push-out test and histomorphometry was performed. Compaction significantly increased ultimate shear strength, energy absorption, apparent shear stiffness, bone implant contact, and peri-implant bone density. The results of this study suggest that compaction may enhance gap healing when osteo-conductive HA porous coated implants are inserted in joint replacements.

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PubMed2003

A new rigid biodegradable anchor for meniscus refixation: biomechanical evaluation.

All-inside repair devices have been developed to overcome the disadvantages of conventional suture techniques (such as vein and nerve damage and increased OR time). The Contour Meniscus Arrow is a second generation of the first biodegradable all-inside implant, the Meniscus Arrow. The aim of this study was to compare the biomechanical properties of the Contour Meniscus Arrow to the first-generation Meniscus Arrow and vertical or horizontal suture techniques. In fresh frozen bovine menisci, initial fixation strength, stiffness and failure mode of four different meniscus refixation techniques (Meniscus Arrow, Contour Meniscus Arrow, vertical and horizontal 2-0 Ethibond suture techniques) were evaluated in a computer-based material-testing machine at a rate of 12.5 mm/s. Vertical meniscus sutures showed the highest initial fixation strength, followed by the horizontal suture technique and the Contour Arrow. The Meniscus Arrow showed inferior pull-out strength. Subjecting the different refixation techniques to cyclic testing decreased the fixation strength in all groups. The modified Meniscus Anchor (Contour Arrow) provides biomechanical properties that are superior (pull-out strength) or similar (stiffness) compared to the first biodegradable all-inside implant, the Meniscus Arrow. The pull-out strength of the Contour Arrow was comparable to the pull-out strength reported for horizontal meniscus sutures in the literature. These biomechanical characteristics of this new implant justify clinical use.

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PubMed2005

Development of a perforated biodegradable interference screw.

PURPOSE: The objective was to develop a perforated biodegradable interference screw to allow for enhanced osseous implant integration without impairing screw stability during insertion. TYPE OF STUDY: Mechanical testing, followed by animal study. METHODS: At first, manual perforation of 8 x 23-mm biodegradable poly-(L-co-D,L-lactide) interference screws was performed, using 3 different perforation patterns (clockwise spiral, counter-clockwise spiral, and parallel perforation), followed by torsional tests. Next, parallel perforated screws (n = 6) and unperforated control screws (n = 6) were applied to the proximal tibia of 12 sheep. The sheep were put down after 24 weeks and the screw site was examined histologically. Subsequently, molding of a parallel perforated screw followed by torsional tests was undertaken. RESULTS: The parallel perforated screw presented a torsional strength insignificantly different from the unperforated control screw and well beyond the reported maximum manual insertion torques of biodegradable interference screws in young human bone. When compared with the regular unperforated interference screw, the molded perforated screw exhibited a torsional strength of 91%, indicating a secure surgical application. In contrast to the unperforated screw, histologic evaluations revealed clear bone ingrowth into the perforations including the core of the perforated interference screw. CONCLUSIONS: Perforated, "cage-like" interference screws may be promising for the acceleration of osseous implant integration into the bone with a very low risk of screw breakage during insertion. CLINICAL RELEVANCE: To ameliorate osseous implant integration and possibly enhance ossification of former implant site in anterior cruciate ligament surgery.

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PubMed2005

Results from a degradable TMC joint Spacer (Artelon) compared with tendon arthroplasty.

PURPOSE: A new spacer for the trapeziometacarpal joint (TMC) based on a biological and tissue-preserving concept for the treatment of TMC osteoarthritis (OA) has been evaluated. The purpose was to combine a spacing effect with stabilization of the TMC joint. METHODS: Artelon (Artimplant AB, Sweden) TMC Spacer is synthesized of a degradable polyurethaneurea (Artelon), which has been shown to be biocompatible over time and currently is used in ligament augmentation procedures. Fibers of the polymer were woven into a T-shaped device in which the vertical portion separates the bone edges of the TMC joint and the horizontal portion stabilizes the joint. Fifteen patients with disabling pain and isolated TMC OA were included in the study. Ten patients received the spacer device and the remaining 5 (control group) were treated with a trapezium resection arthroplasty with abductor pollicis longus (APL) stabilization. The median ages of the 2 groups were 60 and 59 years, respectively. Pain, strength, stability, and range of motion were measured before and after surgery. Radiographic examination was performed in all patients before and after surgery. At follow-up evaluation 3 years after surgery an unbiased observer evaluated all patients. Biopsy specimens were obtained from 1 patient 6 months after surgery. RESULTS: All patients were stable clinically without signs of synovitis. In both groups all patients were pain free. The median values for both key pinch and tripod pinch increased compared with before surgery in the spacer group but not in the APL group. The biopsy examinations showed incorporation of the device in the surface of the adjacent bone and the surrounding connective tissue. No signs of foreign-body reaction were seen. CONCLUSIONS: This study showed significantly better pinch strength after Artelon TMC Spacer implantation into the TMC joint compared with APL arthroplasty.

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PubMed2004

Novel technique for peripheral nerve reconstruction in the absence of an artificial conduit.

The purpose of this study is to promote nerve regeneration across a peripheral nerve gap, using a biologic, tissue-engineered nerve (TEN), containing a high density of viable Schwann cells (SCs) in the absence of supportive foreign materials and a tubular system. Isolated SCs from adult rat sciatic nerve were seeded onto biodegradable constructs and implanted into the backs of nude mice to create TENs. Six weeks later, the constructs were harvested, implanted into surgically created sciatic nerve gaps in rats without supportive artificial conduits and compared with both an autograft group and a silicone conduit group using SCs. Two months later, functional assessment was evaluated by walking track analysis and the implanted lesions were imaged by transmission electron microscopy. The axonal number and sciatic function index of the TEN were significantly higher than those of the silicone group and achieved a comparable level to the autograft group. The results indicate that the large number of SCs within their own extracellular matrix appeared sufficient to enable neuronal growth across a nerve gap in the absence of an artificial conduit and that these circumstances may have a positive effect on the supplement of growth factors from the surrounding tissues of implanted TEN.

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PubMed2002

Functional reconstruction of the non-human primate mandible using recombinant human bone morphogenetic protein-2.

The purpose of this study was to evaluate the long-term functional properties of regenerated bone induced by recombinant human bone morphogenetic protein-2 (rhBMP-2) in segmental bone defects of primate mandibles. The 30-mm defects were created in the mandibles of six young monkeys and the mandibles were fixed with titanium plates. Then 9 mg of rhBMP-2 permeating a poly-D, L-lactic-co-glycolic acid-coated gelatin sponge (PGS) was implanted into the bone defect. Dental implants were placed into the regenerated mandible 20 weeks after surgery, then suprastructures were placed and masticatory force loading was begun 8 weeks after the insertion of the dental implants. Bone formation and the quality of new bone were evaluated radiologically and histologically at 15 and 30 weeks after surgery, and 4 and 24 weeks after masticatory force loading. The resected mandibles were completely regenerated with the rhBMP-2-induced bone. Excellent remodelling and consolidation of new bone were observed after loading. This study demonstrated that the new bone induced by rhBMP-2 in large segmental defects was maintained and functional for at least 1 year. Bone regeneration induced by rhBMP-2 holds promise as a future therapy and may be an effective alternative to autogenous bone grafts for implant dentistry and reconstructive surgery.

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PubMed2004

Bioabsorbable expansion bolt fixation in anterior cruciate ligament reconstruction.

The current study evaluated initial fixation strength of a bioabsorbable expansion bolt compared with interference screw fixation in anterior cruciate ligament reconstruction using a bone-patellar tendon-bone graft. Thirty calf tibial plateaus with adjacent patella and extensor ligaments were used. Bioabsorbable poly-L-lactide interference screws were used for graft fixation in Group I, titanium screws in Group II, and bioabsorbable poly-DL-lactide expansion bolts were used in Group III. The mean force-to-failure (+/- standard deviation) in the three groups was 487 +/- 205 N, 713 +/- 218 N, and 594 +/- 224 N, respectively. The differences between Groups I and II were significant. No statistical differences were found regarding stiffness. Graft damage was significantly less in Group III compared with screw fixation. The fixation concept of an expansion bolt shows similar fixation strength and less graft damage compared with the established interference screw fixation. Because of the total absence of torque forces in contrast to bioabsorbable screws, the risk of implant breakage is minimized.

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PubMed2003

Enhanced bioactivity of a poly(propylene fumarate) bone graft substitute by augmentation with nano-hydroxyapatite.

The bioactivity of a nano-hydroxyapatite-augmented, bioresorbable bone graft substitute made from the unsaturated polyester, poly(propylene fumarate), was analyzed by evaluating biocompatibility and osteointegration of implants placed into a rat tibial defect. Three groups of eight animals each were evaluated by grouting bone graft substitutes into 3-mm holes that were made into the anteromedial tibial metaphysis of rats. Thus, a total of 24 animals was included in this study. Two different formulations varying as to the type of hydroxyapatite were used: Group 1 - nano-hydroxyapatite, Group 2 - micron-hydroxyapatite, with a Group 3 control defect remaining unfilled. Animals of each of the three groups were sacrificed in groups of eight at postoperative week three. Histologic analysis revealed best superior biocompatibility and osteointegration of bone graft substitutes when nanohydroxyapatite was employed. At three weeks, there was more reactive new bone formation in this group when compared to the micron-hydroxyapatite group. The control group showed incomplete closure of the defect. This study suggested that nano-hydroxyapatite may improve upon the bioactivity of bone implant and repair materials. The model scaffold used in this study, poly(propylene fumarate), appeared to provide an osteoconductive pathway by which bone will grow in faster. Clinical implications of the use potential advantages of nano-hydroxyapatite on bone repair and orthopaedic implant design are discussed.

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